Is there an easy way to swap a rigged character for an updated one?
Okay, say you have a main character file complete with rig and extra shapes for your bones. Save your rig and character as a group, and then close.

Open your Scene file, and choose Link from the File menu. Browse to your character file, go to Groups, and choose the group that represents your character.
Once in scene, while selected, choose Object>Make Proxy and then choose your rig name from the menu. This will allow you to then use your rig in pose mode and key frame the bones, while protecting your character mesh from changes. Make your changes upstream in your character file and reopening your scene file will pull the changes in.